Image pickup device having white balance control function

ABSTRACT

There is provided an apparatus having a discriminating circuit to discriminate a magnitude of an occupied area of a single object in a picture plane with respect to a video signal formed by an image pickup element from an object light when a white balance of the video signal is adjusted, wherein by controlling the white balance adjusting operation in accordance with an output of the discriminating circuit, the white balance can be preferably controlled even when the occupied area of the single object is large. Upon macro photographing as well, by making the white balance adjusting operation different from the operation in the ordinary photographing mode, the white balance can be preferably controlled.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an image pickup device and, more particularly,to an image pickup device for controlling a white balance by using animage signal obtained by an image pickup element.

2. Related Background Art

An image pickup device such as video camera, electronic still camera, orthe like has white balance adjusting means for adjusting so that areproduced white color becomes the correct white color. In recent years,a TTL (through the taking lens) adjusting method whereby the whitebalance is automatically adjusted by an output signal of the imagepickup element is frequently used.

FIG. 1 is a block diagram of a conventional image pickup device havingthe white balance adjusting means of the integrating type (averagingtype) TTL method. In FIG. 1, reference numeral 1 denotes a lens; 2 animage pickup element such as a CCD or the like to perform aphotoelectric conversion; 3 a luminance signal processing unit to derivea luminance signal Y from an output of the image pickup element 2; 4 achroma signal processing unit to derive a low frequency component Y_(L)of the luminance signal, a red signal R, and a blue signal B from theoutput of the image pickup element 2; 5 and 6 an R gain control unit anda B gain control unit for changing signal levels of the output signals Rand B of the chroma signal processing unit 4; 7 and 8 matrix amplifiersto derive color difference signals R-Y and B-Y from the output Y_(L) ofthe chroma signal processing unit 4 and outputs R' and B' of the R and Bgain control units 5 and 6; and 9 a modulation processing unit formodulating the output Y of the luminance signal processing unit 3 andthe outputs R-Y and B-Y of the matrix amplifiers 7 and 8 into specifiedsignals and for enabling those signals to be recorded onto a recordingmedium or the like (not shown) or an image to be displayed by a monitor.Reference numerals 10 and 11 denote averaging units to average theoutput signals R-Y and B-Y of the matrix amplifiers 7 and 8 by a fewpicture planes by integrating them or the like. Reference numeral 32denotes a control voltage deriving unit for deriving a control voltagesuitable for the white balance from outputs of the averaging units 10and 11 and for controlling the R and B gain control units 5 and 6.

The operation of the above conventional device will now be describedhereinbelow with reference to FIG. 1.

An object image formed on the image pickup element 2 is first convertedinto an electric signal. An output signal of the image pickup element 2is sent to the luminance signal processing unit 3 and chroma signalprocessing unit 4. The luminance signal Y is derived from the luminancesignal processing unit 3. The low frequency component Y_(L) of theluminance signal and the red and blue signals R and B are derived fromthe chroma signal processing unit 4. The signal Y_(L) is a signal inwhich the red (R), blue (B), and green (G) components are mixed at aratio of 0.30 (R): 0.59 (G): 0.11(B). That is, Y_(L) =0.30R+0.59G+0.11B.The signals R and B among the outputs derived from the chroma signalprocessing unit 4 are sent to the R and B gain control units 5 and 6, bywhich their signal levels are changed to adjust the white balance, sothat the signals R' and B' are generated. The output Y_(L) of the chromasignal processing unit 4 and the outputs R' and B' of the R and B gaincontrol units 5 and 6 are sent to the matrix amplifiers 7 and 8, fromwhich the color difference signals R-Y and B-Y are obtained. Wherein,

    R-Y=0.70R-0.59G-0.11B

    B-Y=0.89B-0.59G-0.30R

The signals Y, R-Y, and B-Y are sent to the modulation processing unit 9and are modulated into specified signal formats such as to enable thesignals to be recorded onto the recording medium or the like or toenable an image to be displayed onto the monitor and are generated.

The output signals R-Y and B-Y of the matrix amplifiers 7 and 8 are alsosent to the averaging units 10 and 11, by which average values of theimage signals of one or more picture planes are obtained. The controlvoltage deriving unit 32 derives control voltages to the R and B gaincontrol units 5 and 6 such that the average signal levels are set to the0 level (that is, R=B=G), thereby adjusting the white balance.

In the above conventional device, however, in the case of the imagepickup of a scene such that a high chroma object occupies almost of thepicture plane, there is a problem such that it is difficult to suitablyadjust the white balance.

Even in the case of the peak method whereby the color difference signalsin the portion where the luminance signal level is equal to or higherthan a predetermined value are sampled and the sampled values are usedto adjust the white balance without using the average values of thecolor difference signals as in the conventional device, the signalswhose levels are equal to or higher than the predetermined level are notalways an achromatic color, so that the white balance cannot bepreferably adjusted. Further, a method in which both of the abovemethods are used in combination is also proposed. Such a method,however, has a problem such that the number of component elements islarge and a construction is complicated and a remarkable improvementeffect is not obtained.

There is also a problem such that when an ordinary object isphotographed, an adequate accuracy is not obtained with respect to thewhite balance in the case of the peak method.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an image pickup device whichcan preferably control the white balance irrespective of thecharacteristics of an object under the circumstances as mentioned above.

To accomplish the above object, according to the invention, as anembodiment, there is disclosed an image pickup device comprising: (a)image pickup means for forming a video signal from an object light; (b)adjusting means for adjusting a white balance of the video signal whichis generated from the image pickup means; (c) discriminating means fordiscriminating a magnitude of an area which is occupied by the singleobject in a picture plane with respect to the video signal; and (d)control means for controlling the operation of the adjusting means inaccordance with an output of the discriminating means.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a construction of a conventional imagepickup device;

FIG. 2 is a block diagram showing a construction of an image pickupdevice of the first embodiment of the invention;

FIGS. 3A, 3B and 4 are flowcharts showing the operation of the device ofFIG. 2;

FIG. 5 is a diagram showing sampling points to determine an occupiedarea according to the device of FIG. 2;

FIG. 6 is a diagram showing a construction of an averaging unit in FIG.2;

FIG. 7 is a timing chart showing waveforms in respective sections inFIG. 6;

FIG. 8 is a diagram for explaining a range of a white balance adjustmentin the device of FIG. 2;

FIGS. 9A, 9B and 10 are flowcharts for explaining the operation of theimage pickup device of the second embodiment of the invention;

FIG. 11 is a block diagram showing a construction of an image pickupdevice of the third embodiment of the invention;

FIG. 12 is a block diagram showing a construction of an image pickupdevice of the fourth embodiment of the invention;

FIG. 13 is a block diagram showing a construction of an image pickupdevice of the fifth embodiment of the invention;

FIG. 14 is a timing chart for explaining an image pickup device of thesixth embodiment of the invention;

FIG. 15 is a block diagram for explaining an image pickup device of theseventh embodiment of the invention;

FIG. 16 is a diagram showing a construction of a peak detector in FIG.15;

FIG. 17 is a diagram showing another example of sampling patterns todetermine an occupied area;

FIG. 18 is a block diagram showing a construction of an image pickupdevice of the eighth embodiment of the invention;

FIGS. 19A and 19B is a flowchart showing the operation of the device ofFIG. 18;

FIG. 20 is a block diagram showing a construction of an image pickupdevice of the ninth embodiment of the invention; and

FIG. 21 is a block diagram showing a construction of an image pickupdevice of the tenth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described in detail hereinbelow.FIG. 2 is a block diagram showing a construction of an image pickupdevice according to the first embodiment of the invention.

In FIG. 2, reference numerals 1 to 11 denote the same component elementsas those shown in the conventional device of FIG. 1. Reference numeral12 denotes an A/D (analog-digital) converter; 13 a microcomputer system;14 a D/A (digital-analog) converter; and 15 a photometry sensor tomeasure the brightness of an external light.

FIGS. 3 and 4 are flowcharts showing the operations of the microcomputer13 in FIG. 2. FIG. 5 is a diagram for explaining the operation todetermine an occupied area in the device of FIG. 2. FIGS. 6 and 7 are aconstructional diagram and a timing chart for explaining the operationsof the averaging units 10 and 11. FIG. 8 is a diagram for explaining alimit range of the white balance adjustment in the embodiment.

The embodiment will now be described hereinbelow with reference to FIGS.2 to 8.

In FIG. 2, the operations of the component elements 1 to 11 aresubstantially the same as those in the conventional device of FIG. 1.The operations of the averaging units 10 and 11 will now be describedwith reference to FIGS. 6 and 7.

In the case of the block 10, the R-Y signal is supplied to the inputside of a switch 16 in FIG. 6. In the case of the block 11, the B-Ysignal is supplied to the input side of the switch 16. The switch 16 isclosed when a signal INTE in FIG. 7 is at the high level. The switch 16is opened when it is at the low level. Only when the switch 16 isclosed, the color difference signals R-Y and B-Y are supplied to anintegrating circuit comprising a resistor 17, a capacitor 19, areference voltage source 20, and a differential amplifier 21. On theother hand, since a switch 18 is closed when a signal RESET in FIG. 7 isat the high level, the charges accumulated in the capacitor 19 aredischarged for the above period of time.

Thus, the outputs of the averaging units 10 and 11 are set to waveformsas shown in SIGNAL in FIG. 7. The average level of each of the R-Y andB-Y signals in one picture plane can be detected by A/D converting theoutputs of the averaging units 10 and 11 by the A/D converter 12 for theperiod of time when SAMPLE in FIG. 7 is at the high level. VD denotes avertical driving signal of the image pickup element 2.

Each of the average values obtained as mentioned above is supplied tothe microcomputer 13 through the A/D converter 12. On the basis of theaverage values, the control voltage to adjust the white balance isderived by the microcomputer 13. The operation will now be describedhereinbelow with reference to FIGS. 3, 4, 5, and 8.

As shown in step in the flowchart of FIG. 3, predetermined values α, β,A, B, C, D, k, l, m, n, L₀, X, Y, R_(c), B_(c), and F₀ are set asinitial values in a memory in the microcomputer. As shown in step 2 inthe flowchart, an output L_(s) of the photometry sensor 15 is readthrough the A/D converter 12 and is divided by the constant L₀, therebyobtaining L (refer to step 3). L₀ denotes a value indicative of theaverage brightness of the outdoor light. When the value L is equal to orlarger than 1, L is fixed to 1 (steps 4 and 5). When L<1, the processingroutine directly advances from step 4 to step 6. In step 6, signals(R-Y)₁ to (R-Y)₅ as R-Y signals and (B-Y)₁ to (B-Y)₅ as B-Y signals atfive positions on the screen shown by "□" in FIG. 5 are read from thematrix amplifiers 7 and 8 through the A/D converter 12.

Outputs (R-Y)_(s) and (B-Y)_(s) of the averaging units 10 and 11 aresubsequently read (step 7) and the control voltages R_(c) and B_(c) ofthe R and B gains to adjust the white balance are set as follows.

    R.sub.c =R.sub.c +1 when (R-Y).sub.s <-α

    R.sub.c =R.sub.c -1 when (R-Y).sub.s >α

    B.sub.c =B.sub.c +1 when (B-Y).sub.s <-β

    B.sub.c =B.sub.c -1 when (B-Y).sub.s >β

The control voltages R_(c) and B_(c) are unchanged, namely, are held tothe initial values in the cases other than the above four cases. (steps8 to ○ 15 )

The control voltage R_(c) of the R gain is set in a manner such thatwhen the value of R_(c) is large, the gain of the R gain control unitincreases and the R signal level rises. The control voltage B_(c) of theB gain is set in a manner such that, on the contrary, when the value ofB_(c) is large, the gain of the B gain control unit 6 decreases and theB signal level decreases. The initial values of the control voltagesR_(c) and B_(c) are set to intermediate values of the ranges which canbe obtained in order to enable the final outputs of R_(c) and B_(c) tobe quickly specified. After the values of the control voltages R_(c) andB_(c) were set as mentioned above, a state of the pickup image isdiscriminated by checking whether a single object occupies a large areaor not (step ○ 16 ). The discriminating method will now be describedfurther in detail with reference to FIG. 4.

In FIG. 4, the constant values k, l, m, and n are added to or subtractedfrom (R-Y)₁ and (B-Y)₁ as R-Y and B-Y signals in the central portion ofthe picture plane (refer to FIG. 5), thereby deriving the followingvalues (steps ○ 16 -1 to ○ 16 -4).

    (R-Y).sub.1+ =(R-Y).sub.1 +k

    (R-Y).sub.1- =(R-Y).sub.1 -l

    (B-Y).sub.1+ =(B-Y).sub.1 +m

    (B-Y).sub.1- =(B-Y).sub.1 -n

Subsequently, P=2 is set to an initial value, the values of (R-Y)_(p)and (R-Y)₁₊ and (R-Y)₁₋ are compared, and (B-Y)_(p) and (B-Y)₁₊ and(B-Y)₁₋ are compared (steps ○ 16 -6 to ○ 16 -9). When either one of theresults of the discriminating steps ○ 16 -6 to ○ 16 -9 is NO, theprocessing routine advances to B, namely, step ○ 19 in FIG. 2. On thecontrary, when all of the discrimination results are YES, a check ismade to see if P=5 or not (○ 16 -10). When P≠5, P is increased by 1 (○16 -11) and the processing routine is returned to step ○ 16 -6 and thesimilar processes are repeated. When P=5, this means that all of thecomparing processes at the five points in FIG. 5 have been finished, sothat the processing routine advances from step ○ 16 -10 to C, that is,to step ○ 17 in FIG. 3.

By the flow of FIG. 4, it is possible to detect whether levels of all ofthe color difference signals at the points 2 to 5 shown in FIG. 5 areapproximate to the level of the color difference signal at the point of1 or not. When all of them are at the approximate levels, it isdetermined that the occupied area of the single object is large.

When the occupied area of the single object is not large, limit rangesa, b, c, and d of the control voltage are set to the initial values A,B, C, and D as shown in step ○ 19 (refer to step ○ 19 and FIG. 8).

On the other hand, when the single object area is large, a flickercomponent F of the external light is first derived from the output ofthe photometry sensor 15 in step ○ 17 and is compared with a referencevalue F₀. When F<F₀, the light source is regarded to be a non-flickerlight source. When F≧F₀, the light source is regarded to be a flickerlight source, namely, a fluorescent lamp. Therefore, when F<F₀, thelimit ranges a, b, c, and d are set as follows.

    a=(X-A)×L+A

    b=(B-X)×L+X

    c=(C-Y)×L+Y

    d=(Y-D)×L+D

(refer to step ○ 18 and FIG. 8). When F≧F₀, they are set such that a=X,b=B, c=Y, and d=D (refer to step ○ 20 and FIG. 8). Those values areconstants to limit the ranges to which the values of the controlvoltages R_(c) and B_(c) can be set by the operations in steps ○ 21 to ○28 . That is, by setting such that

    R.sub.c =a when R.sub.c ≧a is NO

    R.sub.c =b when R.sub.c ≦b is NO

    B.sub.c =c when B.sub.c ≧c

    B.sub.c =d when B.sub.c ≦d

the limit ranges of the control voltages can be set within the rangesurrounded by □klmn shown in FIG. 8.

The control voltages R_(c) and B_(c) obtained as mentioned above aresent to the control units 5 and 6 through the D/A converter 14 and thelevels of the color difference signals are changed. Further, theoperations in steps 2 to ○ 29 are repetitively executed on the basis ofthe changed outputs, so that the white balance can be preferablyadjusted.

The setting of the limit ranges of the control voltages in the firstembodiment will now be described in detail with reference to FIG. 8. Inthe embodiment, a check is made in step ○ 16 in FIG. 3 to see if theoccupied area of the single object is large or not. When the occupiedarea is small, the limit ranges of the control voltages lie within thearea □klmn in FIG. 8 and are set so as to have the values of the controlvoltages R_(c) and B_(c) in a wide range (step ○ 19 ).

On the other hand, when the occupied area is large, it is presumed thatthe high chroma object occupies almost of the area in the picture plane.Therefore, the outputs of the averaging units are largely influenced bythe color of the object and there is a fear such that the white balanceis largely deviated. In the case of such a state, the limit ranges ofthe control voltages R_(c) and B_(c) are made narrower and the positionsof the limit ranges are set to the optimum positions on the basis of theinformation from another sensor or the like. In the embodiment, a checkis first made in step ○ 17 to see if the light source is a fluorescentlamp or not. When it is the fluorescent lamp, the limit ranges are setto □oqms. When the light source is a non-flicker light source, a checkis made to see if the external light is an outdoor light or an indoorlight on the basis of the brightness L_(s) of the external light. WhenL=L_(s) /L_(o) ≧1→L=1, it is regarded that the external light iscompletely the outdoor light and a bluish light source is presumed andthe limit ranges of the control voltages are set to □orlq in FIG. 7. Onthe other hand, for instance, when L≦0.001, the limit ranges are almostset into □osnp. In such a case, since the brightness is fairly dark, theexternal light is regarded to be the indoor light, a reddish lightsource is presumed, and the limit ranges are set. Since the light sourcesuch as a tungsten light source generally becomes reddish as thebrightness becomes dark, it is considered that it is preferably matchedwith the setting of such limit ranges. When L is equal to anintermediate value, the limit ranges move from □osnp to □orlq inassociation with the change in value of L from 0.001 to 1.

The magnitude of the single object area is detected as mentioned above.When it is large, by further narrowing (limiting) the limit ranges bythe information (brightness and flickering amount of the external light)from the photometry sensor 15, the white balance can be adjusted withoutbeing largely influenced by the object color.

In the embodiment, it is also possible to provide a warning apparatus towarn the photographer when the control voltages R_(c) and B_(c) reachthe limits in the limit ranges.

FIGS. 9 and 10 are flowcharts for explaining the second embodiment ofthe invention.

According to the second embodiment, in the same construction as that inthe first embodiment, not only the occupied area on the picture plane ofthe single object but also its chroma is used as a factor for judgment.

That is, in step ○ 16 in FIG. 9, the magnitude of the occupied area ofthe high chroma single object is judged. The processing step ○ 16 isdescribed further in detail in FIG. 10. The operations in steps ○ 16 -1to ○ 16 -11 in FIG. 10 are substantially the same as those in the firstembodiment. In step ○ 16 -(1) in FIG. 10, the absolute value of thecolor difference signal (R-Y)₁ at the point of 1 shown in FIG. 5 iscompared with a constant M. When |(R-Y)₁ |>M, it is determined that theobject is a high chroma object and step ○ 16 -1 follows. When |(R-Y)₁|≯M, step ○ 16 -(2) follows and the absolute value of the colordifference signal (B-Y)₁ at the point of 1 in FIG. 5 is compared with aconstant N. When |(B-Y)₁ |>N, it is determined that the object is a highchroma object and step ○ 16 -1 follows. When |(B-Y)₁ |≯N, it is decidedthat the object is a low chroma object and the processing routineadvances to B, namely, step ○ 19 in FIG. 9.

By the above operations, a check is made to see if the occupied area ofthe single high chroma object is large or small. When it is large, thelimit ranges of the control voltages are further narrowed as shown inthe first embodiment.

Due to this, when the low chroma object which doesn't exert an adverseinfluence on the white balance adjustment occupies the large area in thepicture plane, the range of the control voltages are not narrowed butthe range is narrowed only in the case of the high chroma object whichexerts an adverse influence. Therefore, the more preferable whitebalance adjustment can be performed.

FIG. 11 is a block diagram showing the third embodiment of theinvention. Reference numerals 1 to 15 designate the same componentelement as those shown in the first embodiment. Reference numeral 22denotes an averaging unit having a construction similar to those of theaveraging units 10 and 11. The operation of the third embodiment willnow be described hereinbelow. The operations of the component elements 1to 11, 14, and 15 are substantially the same as those in the firstembodiment.

In the third embodiment, in addition to the (R-Y) value, average valueof (R-Y), (B-Y) value, average value of (B-Y), and output of thephotometry sensor, the signal which is obtained by averaging the Y_(L)output of the chroma signal processing unit 4 by the averaging unit 22is supplied to the microcomputer 13 through the A/D converter 12. Themicrocomputer 13 derives the R, G, and B signals from average signalsY_(LS), (R-Y)_(s), and (B-Y)_(s) of Y_(L), (R-Y), and (B-Y) byexecuting, for instance, the following calculations.

    R=(R-Y).sub.s +Y.sub.LS =R

    B=(B-Y).sub.s +Y.sub.LS =B

    G=(Y.sub.LS -0.30·R-0.11·B)/0.59

A ratio of R to G and a ratio of B to G are calculated from the R, B,and G signals derived as mentioned above. The control voltages R_(c) andB_(c) such that the ratios R/G and B/G are equal to 1 are calculated.The values of R_(c) and B_(c) obtained are sent to the R and B gaincontrol units 5 and 6 through the D/A converter 14, thereby adjustingthe white balance. In the third embodiment as well, the magnitude of thesingle object area is discriminated. When it is large, the limit rangesof the control voltages R_(c) and B_(c) are further limited on the basisof the values of light amount and flickering amount which are obtainedfrom the output of the photometry sensor 15 in a manner similar to thefirst embodiment. Due to this, the white balance can be preferablyadjusted. Further, in the third embodiment, since the control voltagesR_(c) and B_(c) can be immediately calculated from the signals(R-Y)_(s), (B-Y)_(s), and Y_(LS), the embodiment is suitable for a whitebalance adjusting apparatus in an image pickup device such as anelectronic still camera or the like which needs a high quick responsespeed. On the other hand, since the R, G, and B signals are calculatedby once obtaining the color difference signals (R-Y) and (B-Y), theoutput color of the averaging unit can be easily clipped to the highchroma object signal. It is possible to prevent that an adverseinfluence is exerted on the object color. If there is no need to executesuch a clipping process, the signals in the R, G, and B states beforethe color difference signals are derived can be also directly sent tothe averaging units.

FIG. 12 is a block diagram showing the fourth embodiment of theinvention. Reference numerals 1 to 14 and 22 designate the samecomponent elements as those in the embodiment of FIG. 11. Referencenumeral 23 denotes a shutter to decide an exposing time and 24 indicatesan iris.

In the fourth embodiment, the photometry sensor 15 used in the first tothird embodiments mentioned above is omitted and, in place of it, thebrightness of the external light and the flickering amount are measuredby the shutter, iris, and Y_(L) output. That is, the brightness ismeasured and detected by a shutter speed and an iris value when they arecontrolled by the microcomputer 13 and the Y_(L) signal level is aproper level. In addition, output signals are intermittently obtainedfrom the image pickup element 2 and a time-dependent change in the Y_(L)output of the image pickup element 2 is measured, thereby detecting theflickering amount. From the above information, the limit ranges of thecontrol voltages R_(c) and B_(c) when the single object area is largeare decided. In the embodiment, since the photometry sensor 15 can beomitted, the costs can be reduced.

FIG. 13 is a block diagram of the fifth embodiment of the invention.Reference numerals 1 to 15 and 22 designate the same component elementsas those shown in the third embodiment. Reference numeral 25 denotes azoom lens to change a focal distance of an image pickup optical system.

According to the embodiment, in an image pickup device such as,particularly, an electronic still camera or the like in which there isno need to always generate an image pickup signal, when it is determinedthat the single object area is large, a focal distance of the zoom lensis first once set into a short distance upon measurement of the data,that is, in steps 7 to ○ 14 and ○ 21 to ○ 18 in FIG. 3, therebyobtaining a wide lens state. In this state, the control voltages R_(c)and B_(c) are decided. Upon photographing, the focal distance isreturned to an arbitrary focal distance and the photographing isexecuted. Thus, the area of the high chroma object color in the pictureplane can be reduced as small as possible. The data of a more preferablewhite balance adjustment is derived.

FIG. 14 is a timing chart of the main sections in the sixth embodimentof the invention and show switching periods of time and averagingperiods of time of the averaging units corresponding to the averagingunits 10, 11, and 22 in FIG. 13. The sixth embodiment has substantiallythe same construction as that shown in FIG. 2 except the portionsregarding the average values.

As will be also obviously understood from FIG. 14, according to theembodiment, when it is determined that the single object area is large,a part of the averaging period is made intermittent. That is, in such acase, it is presumed that the high chroma object occupies a large areaat the center of the picture plane. Therefore, by using the intermittentpulses for the central portions (for both of the horizontal and verticalscanning periods of time) like the signal INTE in FIG. 14, the samplingperiods of time in such portions are reduced and the influences areprevented and the photographing can be performed at the good whitebalance.

That is, in the embodiment, upon averaging, a weight is applied to apartial area in the picture plane. In place of using the intermittentpulses as mentioned above, it is also possible to apply weights bymultiplying proper coefficients to the color difference signals in thearea of the central portion of the picture plane and to execute theaveraging process.

FIG. 15 is a block diagram showing the seventh embodiment of theinvention. Reference numerals 1 to 15 and 22 denote the same componentelements as those shown in the third embodiment. Reference numeral 26denotes a comparator unit (Y_(L) PEAK detector) to detect whether theY_(L) signal lies within a predetermined level range or not. FIG. 16shows a circuit diagram of the comparator unit 26.

The operation of the seventh embodiment will now be describedhereinbelow. The operations of the component elements 1 to 11, 15, and22 are substantially the same as those in the third embodiment. In thecomparator unit 26, when the Y_(L) signal lies within a predeterminedlevel range, namely,

    E.sub.2 <Y.sub.L <E.sub.1

a high level signal is generated. In the other cases, a low level signalis generated.

The values of E₁ and E₂ in the above case are set so as to correspond tothe signal levels of, for example, 105% and 90% of the Y_(L) level.

That is, when the Y_(L) level lies within a range from 90 to 105%, anoutput signal Y_(L) P of the Y_(L) PEAK detector 26 is set to the highlevel. When the Y_(L) P signal is set to the high level, this means asituation such that the luminance is high and no color saturationoccurs. Therefore, it is considered that the object corresponds to thelow chroma object. Therefore, when the Y_(L) P signal is at the highlevel, the color difference signals R-Y and B-Y are sampled by the A/Dconverter 12 and the sampled digital signals are sent to themicrocomputer 13. The white balance is adjusted on the basis of theoutput signals Y_(L), R-Y, and B-Y of the microcomputer 13. The meansfor deriving the control voltages R_(c) and B_(c) from the signalsY_(L), R-Y, and B-Y is similar to that in the third embodiment.

Further, in the microcomputer 13, the white balance adjusting methodusing the Y_(L) PEAK detector and the adjusting method using theaveraging units are combined and the control voltages are derived so asto compensate the drawbacks of both of the above methods. For instance,there is considered a method whereby when the detection color differencesignals of both of the above methods are selectively used, theinformation of the method by which the lower chroma signal has beendetected is used.

In the embodiment, when it is determined that the single object area islarge, by more preferentially using the color difference signal by theY_(L) PEAK detecting method, for instance, when the difference betweenthe chroma of the color difference signal extracted by the Y_(L) PEAKdetecting method and the saturation of the averaged color differencesignal lies within a predetermined range, by using the former colordifference signal, the influence on the deterioration of the whitebalance adjustment by the averaging method can be minimized.

In each of the above embodiments, the A/D input terminals for the colordifference signals as outputs of the matrix amplifiers 7 and 8 and theA/D input terminals for the average outputs have independently beenprovided. However, as a construction to turn on/off the averagingfunction of the averaging unit, the input signals are directly generatedwhen the averaging function is OFF, and the average outputs and colordifference signals are time sequentially supplied to the A/D converter12, thereby enabling the number of input terminals of the A/D convertercan be reduced.

In each of the above embodiments, the sampling positions of the colordifference signals and the number of sampling positions have been set asshown in FIG. 5. However, it is also possible to discriminate the singleobject area by setting arbitrary sampling positions and an arbitrarynumber of sampling positions.

For instance, in the sixth embodiment, it is also possible to constructin a manner such that thirteen sampling points are set as shown in FIG.17 and intermittent pulses are generated (weights are applied) to onlythe position (either one of the areas 1 to 5 in the diagram) at whichthe area of a predetermined level or higher has been detected.

By changing the positions and the number of sampling points as mentionedabove, even when the single object exists at any position in the pictureplane, the area can be detected and corrected.

In each of the above embodiments, although the color difference signalshave been used to judge the single object area, another signal formatsuch as a luminance signal or the like can be also used.

As described above, according to the devices of the first to sixthembodiments mentioned above, the white balance can be always preferablyadjusted irrespective of the condition such that the single objectoccupies almost of the picture plane.

FIG. 18 is a block diagram showing a construction of an image pickupdevice according to the eighth embodiment of the invention. In thediagram, the same component elements as those shown in the firstembodiment of the invention shown in FIG. 2 are designated by the samereference numerals and their detailed descriptions are omitted here.

In the diagram, reference numeral 1M denotes a macro lens. Themicrocomputer 13 can detect a using state of the macro lens 1M. FIG. 19is a flowchart for explaining the operation of the image pickup deviceof the eighth embodiment. FIG. 19 differs from the flowchart shown inFIG. 3 with respect to the following point. In FIG. 3, the magnitude ofthe single object area has been discriminated by the levels of thesampling points of the color difference signals R-Y and B-Y in step ○ 16. On the other hand, in the eighth embodiment, the using state of themacro lens 1M is detected in step ○ 30 to execute a process similar tothat in step ○ 16 in FIG. 3.

That is, when the macro lens 1M is used or when the image pickup lens isused in the macro region, the processing routine advances to step ○ 17 .Ranges of the possible values of the white balance control voltagesR_(c) and B_(c) are limited in steps ○ 17 , ○ 18 , and ○ 20 in a mannersimilar to the first embodiment. On the other hand, when the macro lens1M is not used, step ○ 19 follows and the ranges of the possible valuesof the control voltages R_(c) and B_(c) are set into a wide rangesurrounded by the points k, l, m, and n in FIG. 8.

The other operations are similar to those in the first embodiment. Inthe case of the macro photographing, it is considered that the occupiedarea of the single object is generally large. Therefore, an effectsimilar to that in the first embodiment can be expected. On the otherhand, since there is no need to execute any special calculation or thelike with respect to the discrimination of the single object area, thereis an advantage such that the processing time can be reduced as comparedwith the first embodiment.

FIG. 20 is a diagram showing a construction of an image pickup device ofthe ninth embodiment of the invention. The microcomputer 13 can obtainstates of an iris 118 and a shutter 117 in a manner similar to thefourth embodiment shown in FIG. 12. In the ninth embodiment as well, ina manner similar to the eighth embodiment, whether the ranges of thepossible values of the control voltages R_(c) and B_(c) are limited ornot is switched in accordance with the result of the discriminationregarding whether the macro photographing is performed or not. At thattime, the states of the iris 118 and shutter 117 are measured in amanner similar to the fourth embodiment as information of the brightnessof the object to determine the limited ranges. The presence or absenceof the flicker is decided by a level fluctuation period of the luminancesignal Y_(L) from the image pickup element 2.

FIG. 21 is a diagram showing a construction of an image pickup device ofthe tenth embodiment of the invention. The microcomputer 13 can controla state of a zoom lens 119 in a manner similar to the fifth embodimentshown in FIG. 13. When the macro lens 1M is used, the zoom lens 119 isdriven to the wide mode side for a period of time when the white balancecontrol voltages R_(c) and B_(c) are being formed. The other operationsare substantially the same as those in the fifth embodiment.

Even by the image pickup devices of the eighth to tenth embodiments asmentioned above, an effect similar to the effect in each of theforegoing embodiments can be expected and the processes can be promptlyexecuted.

What is claimed is:
 1. An image pickup device comprising:(a) imagepickup means for forming a video signal from an object light; (b)adjusting means for adjusting a white balance of the video signal whichis generated from the image pickup means; (c) discriminating means fordiscriminating a size of an area which is occupied by a single object ina picture with respect to the video signal, said discriminating meansdetecting a correlation of color signals on a plurality of samplingpoints which are distributed and arranged on the picture plane; and (d)control means for controlling the operation of the adjusting means inaccordance with an output of the discriminating means.
 2. A deviceaccording to claim 1, wherein said discriminating means uses only thecolor signal of a high chroma.
 3. A device according to claim 1, whereinsaid control means switches an adjustment range by said adjusting meansin accordance with an output of said discriminating means.
 4. A deviceaccording to claim 3, whereinsaid adjusting means includes a pluralityof gain adjusting circuits for relatively adjusting gains of a pluralityof color signals in the video signal which is generated from the imagepickup means and a gain control circuit to determine control voltages ofsaid plurality of gain control circuits in accordance with colortemperature information, and said control means switches limit ranges ofthe control voltages in accordance with the output of saiddiscriminating means.
 5. A device according to claim 4, wherein saidcontrol means sets the limit range of the control voltage into a firstrange in the case where it is determined by the discriminating meansthat the size of an area which the single object occupies in the pictureplane is smaller than a predetermined size, and the control means setsthe limit range of the control voltage into a second range narrower thanthe first range in the case where it is determined that the size whichthe single object occupies in the picture is larger than thepredetermined size.
 6. A device according to claim 5, further comprisingflicker detecting means for detecting a flicker of a light source,andwherein said control means can changeably set the second range inaccordance with an output of the flicker detecting means.
 7. A deviceaccording to claim 5, further comprising generating means for generatinginformatiion according to the brightness of the object,and wherein saidcontrol means can changeably set the second range in accordance with anoutput of said generating means.
 8. A device according to claim 7,wherein said generating means includes a photometry circuit whichgenerates an output at a level corresponding to the brightness of theobject, and said control means variably sets the second range inaccordance with a magnitude of the output level of the photometrycircuit.
 9. A device according to claim 8, wherein said control meansswitches the second range in accordance with the presence or absence ofa fluctuation of the output level of the photometry circuit.
 10. Adevice according to claim 7, wherein said generating means fetches irisinformation and shutter speed information of said image pickup means andgenerates information according to the brightness of the object inaccordance with said iris information and said shutter speedinformation.
 11. A device according to claim 1, wherein said adjustingmeans includes signal processing means for forming color temperatureinformation in accordance with levels of a plurality of color signal inthe video signal which is generated from said image pickup means, andsaid control means switches extracting formats of said plurality ofcolor signals by the signal processing means in accordance with anoutput of the discriminating means.
 12. A device according to claim 11,wherein said control means controls such that said signal processingmeans extracts an average level of said plurality of color signals ofthe whole picture plane in the case where it is determined by thediscriminating means that a size of an area which the single objectoccupies in the picture is smaller than a predetermined size,and saidsignal processing means extracts only said plurality of color signals inthe portion where a luminance level in a predetermined range in the casewhere it is determined that the size which the single object occupies inthe picture is larger than the predetermined size.
 13. A deviceaccording to claim 11, wherein said control means controls such thatsaid signal processing means extracts a relatively large amount of saidplurality of color signals in the edge portion of the picture plane thanthe central portion thereof in the case where it is determined by thediscriminating means that a size of an area which the single objectoccupies in the picture is larger than a predetermined size as comparedwith case where it is determined that the area which the single objectoccupies is smaller than the predetermined size.
 14. A device accordingto claim 1, wherein said adjusting means includes signal processingmeans for forming color temperature information in accordance withlevels of a plurality of color signals in the video signal which isgenerated from the image pickup means, and said control means controls afield angle for picking up an image of said image pickup means inaccordance with an output of the discriminating means.
 15. A deviceaccording to claim 14, wherein said control means sets the field anglefor picking up the image to a wide angle in the case where it isdetermined by the discriminating means that a size of an area which thesingle object occupies in the picture is larger than a predeterminedsize as compared with the case where it is determined that the areawhich the single object occupies is smaller than the predetermined size.16. An image pickup device comprising:(a) image pickup means for forminga video signal from an object light; (b) adjusting means for adjusting awhite balance of the video signal which is generated from the imagepickup means, said adjusting means including signal processing means forforming color temperature information in accordance with levels of saidplurality of color signals in the video signal which is generated fromthe image pickup means; (c) detecting means for detecting whether amacro photographing is performed by the image pickup means or not; and(d) control means for controlling the operation of the adjusting meansin accordance with a detection result of said detection means, saidcontrol means controlling a field angle for picking up an image of saidimage pickup means in accordance with whether the macro photographing isperformed by the image pickup means or not.
 17. A device according toclaim 16, wherein said control means switches an adjustment range by theadjusting means in accordance with whether the macro photographing isperformed by the image pickup means or not.
 18. A device according toclaim 17, wherein said adjusting means includes a plurality of gainadjusting circuits for relatively adjusting gains of a plurality ofcolor signals in the video signal which is generated from the imagepickup means and a gain control circuit for determining control voltagesof said plurality of gain control circuits in accordance with colortemperature information,and wherein said control means switches limitranges of the control voltages in accordance with the detection resultof said detection means.
 19. A device according to claim 18, whereinsaid control means sets the limit range of the control voltage into afirst range in the case where the macro photographing is not performedby the image pickup means, and the control means sets the limit range ofthe control voltage into a second range narrower than the first range inthe case where the macro photographing is performed.
 20. A deviceaccording to claim 19, further comprising generating means forgenerating information according to the brightness of the object,andwherein said control means can changeably set second range in accordancewith an output of the generating means.
 21. A device according to claim16, wherein said control means sets a field angle for picking up animage of said image pickup means to a wide angle in the case where it isdetermined by the discriminating means that a size of an area which thesingle object occupies in the picture larger than a predetermined sizeas compared with the case where it is determined that the area which thesingle object occupies is smaller than the predetermined size.
 22. Animage pickup device comprising:(a) image pickup means for forming avideo signal from an object light; (b) adjusting means for adjusting awhite balance of the video signal which is generated from the imagepickup means; (c) discriminating means for discriminating a size of anarea which is occupied by similar color or similar brightness in apicture with respect to the video signal, said discriminating meansincluding an extracting circuit for extracting a plurality of videoinformation in a plurality of different areas in the picture and adetection circuit for detecting a correlation among the plurality ofvideo information; and (d) preventing means for preventing saidadjusting means from using a video signal in the area occupied by thesimilar color or similar brightness in accordance with an output of thediscriminating means.